Construction on the Pentagon started on Sept. 11, 1941, in the midst of World War II. The five-sided design was chosen to accommodate existing roads around the building's original site near Arlington National Cemetery; a different site was ultimately picked, but the design was kept, according to the History Channel.

Hillary Clinton did not have a State Department email account while she served as America's top diplomat, a senior state department official said Monday, and instead used a personal email account during her four years on the job.